Re: [Xen-devel] [PATCH RFC 00/12] xen-block: indirectdescriptors

From: Jan Beulich
Date: Thu Feb 28 2013 - 05:49:18 EST

>>> On 28.02.13 at 11:28, Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
> This series contains the initial implementation of indirect
> descriptors for Linux blkback/blkfront.
> Patches 1, 2, 3, 4 and 5 are bug fixes and minor optimizations.
> Patch 6 contains a LRU implementation for blkback that will be needed
> when using indirect descriptors (since we are no longer able to map
> all possible grants blkfront might use).

Considering this, ...

> Patch 7 is an addition to the print stats function in blkback in order
> to print information regarding persistent grant usage.
> Patches 8, 9, 10 and 11 are preparatory work for indirect descriptors
> implementation, mainly make blkback use dynamic memory and remove the
> shared blkbk structure, so each blkback instance has it's own list of
> free requests, pages, handles and so on.
> Finally patch 12 contains the indirect descriptors implementation.
> I've also pushed this series to the following git repository:
> git:// xen-block-indirect
> Performance benefit of this series can be seen in the following graph:

... would you happen to also have a comparison with using
indirect descriptors but not persistent grants? IOW I'm
wondering about the hit rate on the persistently mapped
grants, especially when blkfront really saturates the added


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